Aircraft landing gear



Sept. 15, 1953 Q BRUKNER 2,652,215

. AIRCRAFT LANDING GEAR Filed D90. 17, 1946 2 Sheets-Sheet 1 Fig. 3

- PATENT ATTORNEY S p 1953 c. J. BRUKNER 2,652,215

AIRCRAFT LANDING GEAR Filed Dec. 17, 1946 2 Sheets-Sheet 2 Patented Sept. 15, 1953 2,652,215 AIRCRAFT LANDING GEAR Clayton John Brukne The Wac Aircraft Ohio r, Troy, Company, a corporation of Ohio, assignor to Application December 17, 1946, Serial No. 716,829 3 Claims. (01. 244-50) gear adapted for the operation of aircraft under side drift conditions.

The landing and take-off of aircraft under side drift or cross-wind conditions has presented many problems and has been the cause of nuniero us aircraft accidents. Inasmuch as the number and direction of the of side drift or a cross-wind. As this angle between the wind direction and that of the runway becomes greater, the landings or take-offs under these conditions become increasingly diflicult.

In the case of airplanes provided with steerable nose wheels, the side forces exerted upon the pilot controls are frequently of such magnitude as to wrench the control away from the pilot at the instant of landing. This condition has been known to be so severe in certain aircraft that side drift and cross-wind landings and a number of proposed arrangements have been suggested and tested. One of the proposed solutions has been to pre-set all of the landing wheels into a the main wheels, when directionally deflected or at angles with respect to said landings and take-offs.

It is accordingly a major object of the present lnvention to provide an improved landing gear landing characteristics. Other objects and advantages will occur to those skilled in the art after reading the present specification and the nals 24 and.25.-

form of the resilient and hydraulic damping;

means interconnecting the main landing gear wheels.

Referring now to Fig. 3 the numeral 'lu -indie cates, in part, the fuselage outline of an airplane to which the improved landing gear of this in vention is applied. The fuselage .has a-cockpit.

portion Hia from which the airplane is controlled which it may be steered upon in flight and from the ground, upon which it is supported by a landing gear of the tricycle type comprising thenose wheel. ll andthe main wheels l2'and l3. As is usual in airplanes having. this type landing gear, the center ofgravity will be disposed slightly forward of the main wheels l2- and i3, and an appreciable distance to the rear of the nose wheel II, as indicated in Fig. 3.

Thenose wheel ll is pivotally supported from the fuselage frameworkiti -by .an approximately vertically disposed. post journal the landing gear. member lG-is adapted to rotate or swivel. In an actual installation a rearward inclination of-. some,9.degrees gave satisfactory results.- The member is preferably has pivoted thereto the wheel-carrying member l'i' upon which the landing wheel I l is rotatably mounted, and resilient means interposed between members IE5 and I1 absorbs. vertical.-.impacts or shocks which the nose wheel ll may be subjected to. This wheel mounting need not however be of the leveredsuspension typebut may also be of the more common telescopic type of mountings using nut-cracker or other steering connections. In the upper end of the landinggear member [6 there isattached a-forwardly diverging. yoke member. 18 at the forward. ends of which. there arepivotally mounted the cable sheaves l9 and 28,. adapted to. receive the steering cables.-2l and '22, respectively, a forwardterminal of each of. which is anchored to the fuselage framework NJ The main orrear wheels Hand 13 are-attached to theaircraft framework Mwthrough the medium of the cross tube 23, to the laterally disposed ends of-which arefitted thepost jour Each main landing wheel is provided. with a levered suspension unit comprising. the upper membersZG and. 21, respectively, having strut portions rotatable withinthe post journals Hand 25, and. are each provided with wheel-carrying levers, 28 and 29, which are provided. with resilient shock-absorbing meansto prevent folding of the members 26-2 8 and.21--29 about their common pivots 30 and 31;, respectively. Each strutmember 26 and 21 has attachedthereto forwardly directed ears-or lugs 32 and 33as well asinwardly andelaterallydirectedears 34-and 35. Pivotally disposedbeetween. the forward ends.;of the ears 32-and 33 there is provided a dampingunit 36 and the connecting push-pull rods 3'l and 38, the details and operation of which will be hereinafter .more fully explained.

The opposed the ears. Gland inwardly directedv terminals of v have attached thereto. a terl5 Within which sheaves engage and. ride up on minal of each of the cables 39 and M! which cooperate with the above mentioned cables 2| and 22. Within the cockpit Illa of the airplane there is preferably provided a pair of control wheels ll and 42 as also indicated in Figs. 2 and 3, and their respective shafts Ma and 42a are rotatable within the journal portions 43 and M at the upper endsofthe columns 45 alfldflfis These columns are-provided with lowenpivot portions 41 and 48 which are rotatably mounted upon the fuselage structure such that the columns can be rockedrwlthin fore and aft vertical planes about the same transverse horizontal axis A--B. Controlcables 49,556, El, and 52 are attached to -the.respective.columns 45 and 46 above and below the horizontal axis A-B, and are connected to certain of the airplane flight control surfaces, as more fully described below. Sprockets 53 and are connected to the forward ends of the shafts Ma, and 42a respectively and are engaged by chain pprtionsof the previously; referred'gto cables 2| and 22-.- The: sprockets 53 and54 are usedto; engage short lengths of; chain; in the up per runs of cables 2| and 22 m get positivadrive through two full revolutions of .the control wheel. Somewhat to the-rear and above the levers or ears 34 and 35, the cables-=39-;andAdrunnveif; the sheaves 55 and 56 and thenextend forwardly engaging the additional sheaves 51. and 58.5and; terminating in the fittings 5510; and Gila-which are pivotally attached to the axesrofythe floating; take-up sheaves 59. and 60. These take' up the-,cables 2| and 22, being heldin engagement therewith by ;the. tension in the cables 39 and; dfi and unlike the sheaves. 55, .56, 51 and 5.8,;which; are-mounted. for rotation upon the aircraft, structure upon. fixedaxes, the take-up.-sheaves 59..-.and .60 are; freeto follow paths which are-determined by. -the-, forces to which the cables 2|, 22, 39 and 40..are-. subjected.

The cables 21 and -22, in .extendingoutwardly: and rearwardlyzfrom-the nose .wheelyokesheaves; i9 and legengagethe guide sheaves' fil and 62 from whichthey exte nd' rearwardly to engage the take-up sheaves-59 and-Gil and from whiqh they extend upwardlyto the respective control units 4| and 42; Additional guide sheaves 63a. 63b and 630 are engaged by theoableil asit extends up to and around; the; control sprocket 53, andsimilar guide sheavest la 65b and-1.64s; are engaged bythe cable22 as -it extends up tov and around thecontrol. sprocket 54.. These-guide; sheaves are preferablymounted-such that the; cable contacting portions are tangent to the; axis.- A-B-, about which -the;columns .45 andsdli are: adapted to rotate, and thereby-permit such =rota-.-- tion of the columns without subjectingthecable sets 2l -39 and -22;-,-flfi-.to tensioning or'slackenling. It will also be-noted that the cableswZl and 22 may cross beneath the; respective. control sprockets 53.and-1.54 asindicatedat 22a;in Flg; 1, but 1 whilethis schematic arrangement is on tirely feasible, any possible interference duet-to: crossing can be; avoided by; adifferent routing ,of the .cables as design considerationsmay.require whereby they permit thectransmission ofaoon trol-forcesfrom theawheels M and 42, and it will. be understood that. the adjacentends of the. cables 2| and' 2'2 will'be-connected asiat- 2l -22 along the axis A-B,- and intermediate the&co lumns Mi and 56,: to form in effect togfither with the chain portions, a singlecontinuous cableway V The control -mechanism.-.for- .the present landing gear is cooperatively;interconnected Wlthythfir and I22 which are guided by the sheaves I23 and I24 respectively. tobring the air they are connected to the ground control cables 2| and 22 by the connectors I25 and I26, respectively. In a preferred form of airplane control to which the present landinggear-is particularly adapted the control cables 49, 50, 5| and 52 extend rearwardly, through suitable control mechanism, to a pair of drooping ailerons and to the elevator surfaces, the latter being actuated by rocking movements of the control columns 45 and 46 about the transverse axis A-B. The control cables I2I and I22 preferably extend rearwardly to control mechanism by which they are connected to both the ailerons for conven-' tional differential operation thereof forlateral control, and to the rudder surfaces for directional control. The present landing gear is accordingly particularly adapted for use in an airplane in which the lateral and directional flight controls may be operated from a single control device, andthe directional ground control or steerable nose wheel may be operated from the same manual control device.

A preferred form of the damping device 35 indicated in Fig. 1, is shown in detail in Fig, 4, and consists principally of a central tubular body portion 65 threaded at 65a and 65b to engage the end portions 66 and 61. The central portion 65 is intermediately bored at 650 to provide a cylinder within which a double piston unit 68 having pistons 69 and 10, is adapted to reciprocate, the pistons being interconnected by the piston rod H and provided with suitable packing seals 69a and a. Across the central portion of the cylinder pistons 69 and 10 are reciprocated within the cylinder 650. The central wall 12 may preferably be positioned and anchored to the cylinder 65 by the threaded stud 12d. I -A fluid reservoir 13 is threadedly attached to the transverse wallmember 12 asat' 13a, and to the cylinder wall 65 by the threaded bushing 65d. The reservoir is provided with communicating ports and check valves 14 and 15 on either side of its central dividing wall 13b which communicate respectively with the cylinder chambers 12b and 12c. A combined filling plug 15 and check valve 15a is provided through theupper end of the reservoir 13 to permit filling and venting as a result of dropping of the fluid level due to leakage past the piston packings.

' The end units 66 and 6 portions are each provided with reduced diameter portions 690 and 100 and shouldered portions 1012 pressed springs are located washers 16a and'11d, which at the normal central position of the dual ing runway with a cross-runway wind coming obtion of the cars 32 and 34 shown in Fig. 1, the rotation being in the same direction but apart. Movement of the car 32 is resiliently opposed by the compression spring 11, Fig. 4, within the combined centering and damping device 36, and is within the chamber 120, through the metering orifice 12a, into the chamber 121). As this resilient and non-reactive opposition to movement at 2I-22 rearward run of the cable 22 which is also simia oe-2:52:15

with tthegrestrained icontrolz sprocketaM l and;also by itsiconnection 21-1-22 with the grearwardisimie larly :restrained: portion of {the 1-.cable. 2i! the. ten- .sioned cable 22;tends to straightenoutbetween sheavesjland 54a and to'vpuil the-floating sheave SOs-upwardly andforwardly to; the: samelzlextent to which thecable wlhas beenslackened orpayed out; i as previously described. The arrangement of the mechanism-is such that"; thee angle A through which the noserwheel, ltisrrotatediinto its position; I l ai is appreciably greaterrthanythe angles B or '0; through which the-main wheels I 2 and? [3 have been rotated. The-settingrof the nose wheel toa greaterrangle than-7, the main wheels serves to ;assistin more ,rapidlyrbringing the-airplane into the desired-heading(direction .of its line of motion.

This automatic setting of the 1 1108611, wheel: 1 l willrbe-l caused by lateral deflection forces on either one or both of the main'wheelsl2gandil3i It h-as the distinct advantage thatit can auto-:

matlcally set-or position the nose wheel I i with:

out required movement of the pilot control; as only a-relatively small holdingforce;wou1d,nec essarily be-applied-to the control wheels-Al and 42 to-cause the cablesto automaticallyisteer the noserwheel by deflection of the-main wheels; This has the effect of placing thenose wheelinto anew mid-position with respect to the pilot'control in which it" is correctly set for the-landing, andfrom which new mid-positionthe-pilot can continuously steer-the nose wheel to-ei-ther; side aselanding conditions may require. Another advantageous result which is accomplished by this improved arrangementis derived-from the move ment-ofthe .nosewheel through agreater angle than therear wheels-in sucha manner that any desirable? air control which is made-thy the pilot can be exercised without positioning the front wheel in a direction'which is-adverse to the drift ing direction of the aircraft;- In other-words; in ailanding which would cause: the-landing gearto assume the dotted line position shown; in Fig.1 2', in theieventthe pilot at the instant-,oilandi-ng found: it necessary to apply aqcorrectivecontrol-force to-his air controls, to laterally:correct any Slight transverse unbalance which-may result from drifting contact with theground; he could accomplish this without rotating the; nose iwheelinto a: position in, which it would beiacross the direction in which-theairplanewas. drifting. Similarly anycorrective rudder-movee mentltotheleft would cause the nosewheel l Ito. move through a relatively smaller angle from the optimum position than it would without the automaticsetting provided by the, present. landing gear arrangement.

As the airplanes heading is steeredinto'the: direction of its travel, the side forces on ,the rear. wheels proportionately decrease so that the compression spring H in the damping-device 36;gr a djuallyi overcomes the side forces applied to" the wheels ,l-Zand l3, as well as the. resistance'tothei movementof the piston 10. As this continues; the main wheels are restored to their; centralfore andaftdirection and the relative-tensioning of .the. cables 39 and 40 is releasedand theyrbe ciome restored to their initial neutralrposition; Thisvhasthe eiifect of returning the nosewheel' l l to its normal, mideposition with respect to the air controls and in the event it requires-any: further, corrective adjustment thepilot isFfre to steer thenoser wheel concurrently withhisair; controls during the period in which the airplane; is completing its landing run. It pwillaccordingly;

ernot d that w enat e siderd ift-=;causes;swivei: lingof; the rear wheelsyagainst-the: sti a d ener y absorbing-restra nt 0 heunittfi; thenos wheel is swivelled through-acreataranglerwith out any movementoithe pilots hand wheel; thus it is possible. for the; pilot to-- use instinctive mo mentarvyropposite control should a wing dinwith out pausing-y any serious, adverse effiect upon :the directives position of the nose wheel.

The resilient; hydraulic damping devicefifu; is shown in 4v inits central neutral portiona It will; be noted; that through this; device; and ;the push-pmlrods 3] and 38.:thegears y32;and;33;.olj thejrespectivelanding gearrunitsare 'rigidlyintera connected in such'manner-that-the;wheels IZfand l 3 :are-at. all times caused to track 'alongparallel planes. As the wheell 2 is causedto-move through the angle B,;,into the dottedqline,position; l2q, thepushepull rod 3;! isdrawn toward the left side of-the airplaneon which the wheel i2is mounted and'since the unit-.35 is fixedly attached-through theiweb 3130 to the; cross :tube -23, the spring l1 will-"be caused tobe compressed by-the washer 10das it moves toward the reduced diameter-pertion Blmagainst which is, disposed the washer 1m; As; the shouldered portion- 691)? however causes .the washer 16a to moveaway= from; the abutment tea the spring I 6 ,is; moved toward the right with the shaft 690 without permittin 'rthe spring 16 -to extend andgthusiexert Precampression-eenergyto assist; further movement- ;in; opposition to the restraint of sprin ;1].; the piston 10: moves toward the central partitiom 12 the displaced fluid iSiOlCBdithlQllgh the annular metering. orifice I12a serving to oppose: andgdamp the movements The4=reservoir 13sisgkept rea onably filled with hydraulic fluid and inthgevent of slight leakage past the packings in the-pistons BSand 'Iflrepelenishing-flow is permitted past the check valves '14 1and;15-to-:replace anyrfiuidwhich: may: have become lost: The fitting 151 ;atthe-top; of the reservoir 3 provides for fillingofthe reservoiri-and includesqthe check-valve 15a which pre vents-spilling of thafiuidwhenthe main landing: gears are retracted: about the axisof? the-cross tube 23, and also permits venting ;of-the;;inte rior of the. reservoir:

It :will; accordingly 'be noted: that; a relativel effective mechanismris providedtocause positioning of the nose wheel by displacement of; the; main wheels without effecting the neutral posia tion of the flight controls, or thepilotcontrols; In otherqwords, this automaticpositioningis accomplished while the flight controlis held-sta e. tion-a-ry "by: the =Di10t without: disturbing ,his man: dling of "that control. It also has the effect; of placing the nose wheel into a new mid position; in thegoptimum attitude for aside drift landing and from-whichmid-position thepilot'can apply any necessary further steering movementsin the same-manner that he would lithe-nose wheelhad notbeemdisplaced-J three wheel tricycle adapted for useinea landing-gear having one or more rear main wheels, .as well-as landin gears havingmore thanone forward or nose wheel for the; nose wheels.

wheel and at 23 .for the: main'rear While 1 the present-invention has been shown; anddescribedas applied to -a, landing gear, it: is equally;

The improved landin -v g r l o pro; vides a-very satisfaetoryyrestraint against swivel other, that is to say, neither spring urges the motion beyond the neutral position when returning to neutral. Therefore, a very positive central springs until sufiicient side load is developed to cause displacement from this neutral position.

Accordingly, with the present improved landing gear and operating mechanism as described pilot may continue to exercise his some precise instant during a drifting landing and to temporarily trust his craft to the mercy of air gusts and ground irregulari- Or, stating this advantage in other lancastering forces in drift urge it to do so. Were this done in a conventional tricycle landing gear with a Wheel-steered nose wheel, it would result in a movement of the lateral air controls to add to the tipping or unbalancing which might result with the ground. In conmovement of the rear wheel, with the following two advantageous results; (1) The nose wheel will freely caster-steer to the direction of its motion; and (2) The remaining cable travel which is not here used to over-steer the nose wheel will produce rotation of the control wheel, and in the direction which produces lateral air control to subtract from the tipping which may result from drifting contact with the vide a very distinct and advantageous improvement in safety and in simplified flying.

Other forms and modifications of the present invention both with respect to its general arrangement and the details of its respective parts come Within the scope as more particularly claims.

I claim:

resiliently and non-reactively centered in their normal aligned central positions.

2. In an aircraft landing gear including a pair of laterally spaced main wheels, said main wheels be ng pivotally mounted upon the aircraft for a result of preventing further expansion of abutment on said rod member.

3. In an aircraft having a pair of laterally spaced swivelling landing gear units, a non-reacin said cylinder in a given direction: causingengagement of said transverse abutment'on said cylinder with said sliding disc andhcompression ofione of said springs on1y,-the othersaid spring being prevented from further expansion by engagement of its sliding disc member -with-said corresponding stop portion on said rod member.

CLAYTON JOHN BRUKNER.

References Cited in thefile of this patent UNITED STATES PATENTS Number Number Name Date .McLa-ren et-al W Mar. 28,:1944 Koppen Aug 1,:1944 Jamisonr Feb. 1, 1949 Hoobler -Apr. 4,4950 FOREIGN PATENTS "Country Date Australia 'Feb. 22,1940 

